import logging
from datetime import timedelta

import homeassistant.helpers.config_validation as cv
import requests
import voluptuous as vol
from homeassistant.components.sensor import (CONF_STATE_CLASS,
                                             DEVICE_CLASSES_SCHEMA,
                                             STATE_CLASSES_SCHEMA,
                                             SensorEntity)
from homeassistant.const import (CONF_DEVICE_CLASS, CONF_NAME, CONF_UNIQUE_ID,
                                 CONF_UNIT_OF_MEASUREMENT, STATE_UNKNOWN)
from homeassistant.helpers.config_validation import PLATFORM_SCHEMA

CONF_PROMETHEUS_URL = 'prometheus_url'
CONF_PROMETHEUS_QUERY = 'prometheus_query'
SCAN_INTERVAL = timedelta(seconds=60)

_LOGGER = logging.getLogger(__name__)


PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
    vol.Required(CONF_PROMETHEUS_URL): cv.string,
    vol.Required(CONF_PROMETHEUS_QUERY): cv.string,
    vol.Required(CONF_NAME): cv.string,
    vol.Optional(CONF_UNIT_OF_MEASUREMENT): cv.string,
    vol.Optional(CONF_STATE_CLASS): STATE_CLASSES_SCHEMA,
    vol.Optional(CONF_DEVICE_CLASS): DEVICE_CLASSES_SCHEMA,
    vol.Optional(CONF_UNIQUE_ID): cv.string,
})


def setup_platform(hass, config, add_entities, discovery_info=None):
    """Set up the sensor platform."""
    prom_data = {
        'url': str(config.get(CONF_PROMETHEUS_URL)) + "/api/v1/query",
        'query': str(config.get(CONF_PROMETHEUS_QUERY)),
        'name': str(config.get(CONF_NAME)),
        'unit': str(config.get(CONF_UNIT_OF_MEASUREMENT)),
        'state_class': str(config.get(CONF_STATE_CLASS)),
        'device_class': str(config.get(CONF_DEVICE_CLASS)),
        'unique_id': str(config.get(CONF_UNIQUE_ID)),
    }

    add_entities([PrometheusQuery(prom_data)], True)


class PrometheusQuery(SensorEntity):
    """Representation of a Sensor based on Prometheus"""

    def __init__(self, prom_data):
        """Initialize the sensor."""
        self._url = prom_data["url"]
        self._query = prom_data["query"]
        self._attr_name = prom_data["name"]
        self._state = None
        self._attr_native_unit_of_measurement = prom_data["unit"]
        self._attr_state_class = prom_data["state_class"]
        self._attr_device_class = prom_data["device_class"]
        self._attr_unique_id = f"${prom_data['url']}$${prom_data['query']}"
        if prom_data["unique_id"] is not None:
            self._attr_unique_id = prom_data["unique_id"]

    def update(self):
        """Fetch new state data for the sensor.
        This is the only method that should fetch new data for Home Assistant.
        """
        try:
            response = requests.get(self._url, params={'query': self._query})
            if response:
                results = response.json()['data']['result']
                if len(results):
                    self._attr_native_value = results[0]['value'][1]
                else:
                    _LOGGER.warning('Empty result returned for query %s', self._query)
                    self._attr_native_value = STATE_UNKNOWN
            else:
                self._attr_native_value = STATE_UNKNOWN
        except requests.exceptions.JSONDecodeError:
            _LOGGER.exception("Unable to decode response from Prometheus")
            self._attr_native_value = STATE_UNKNOWN
            pass
        except requests.exceptions.ConnectionError:
            _LOGGER.error("Unable to connect to the Prometheus server at %s", self._url)
            self._attr_native_value = STATE_UNKNOWN
            pass
        except Exception:
            _LOGGER.exception("Error when retrieving update data")
            self._attr_native_value = STATE_UNKNOWN
            pass

        self._attr_state = self._attr_native_value